Method for refining phosphoric acid desulfurization slag directional recycling resource utilization

Abstract

The application relates to a method for refining and cyclically utilizing phosphoric acid desulfurization slag, which comprises the following steps: mixing desulfurization slag and a leaching agent to obtain a first suspension, wherein the leaching agent comprises an organic solvent, and the organic solvent comprises methyl isobutyl ketone and a fatty alcohol; performing first filtration on the first suspension to obtain a first filtrate; sequentially performing desulfurization treatment and second filtration on the first filtrate to obtain a second filtrate; and performing back extraction on the second filtrate to obtain phosphoric acid. The method provided by the application can realize cyclic utilization of materials, is simple in process, easy to realize industrialization, and has high economic and environmental benefits.

Description

Technical Field

[0001] This application relates to the field of desulfurization slag resource utilization, such as a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization slag. Background Technology

[0002] With the increasing demand for electronic-grade and food-grade phosphoric acid, as well as the rapid development of the lithium iron phosphate battery industry, phosphoric acid purification and refining has become an important industry in the phosphoric acid chemical industry. Refined phosphoric acid desulfurization residue is a byproduct of phosphoric acid purification and desulfurization.

[0003] The main component of refined phosphoric acid desulfurization slag is calcium sulfate, which is also the main component of phosphogypsum. Currently, the world's annual wet-process phosphoric acid production capacity is close to 300 million tons (based on P2O5), and this industrial chain alone emits nearly 1.5 billion tons of phosphogypsum annually. However, the actual utilization rate of phosphogypsum is less than 5%, and large quantities of phosphogypsum are stored in the open, occupying significant amounts of land and causing environmental pollution from leachate. Meanwhile, the world's annual industrial phosphoric acid production capacity is approximately 60 million tons (based on P2O5), with desulfurization slag production of about 20 million tons, greatly increasing the pressure on phosphogypsum disposal.

[0004] Currently, the comprehensive utilization of phosphogypsum mainly focuses on cement retarders, roadbed materials, and building gypsum powder. This utilization method is not only energy-intensive but also cannot be produced on a large scale continuously, and it will also cause secondary pollution to the environment. In addition, phosphogypsum has many impurities and low whiteness, which leads to relatively low enthusiasm for its utilization in industry.

[0005] CN106744769A discloses a method for producing feed-grade calcium phosphate and co-producing ammonium sulfate using phosphogypsum. This method uses phosphogypsum, a byproduct of phosphate fertilizer plants, as raw material. The phosphogypsum is defluorinated and activated, and a reaction aid is added to react with ammonium dihydrogen phosphate. The product is then prepared through filtration, concentration, crystallization, and drying, and feed-grade calcium phosphate is produced, co-producing industrial ammonium sulfate. CN115180598A discloses a comprehensive utilization process for phosphogypsum, including the following steps: (1) phosphogypsum is purified to obtain calcium sulfate. The calcium sulfate is slurried and then mixed with organic acid and a diluent for extraction and phase separation. The resulting aqueous phase is dilute sulfuric acid. (2) The oil phase obtained from the phase separation is back-extracted with phosphoric acid, and the resulting aqueous phase is sent to the calcium phosphate production system. The oil phase is returned to step (1) for mixing and extraction. Although the above methods can utilize phosphogypsum to produce some products, the resource utilization of phosphogypsum is not high, and the products cannot achieve high yield and high purity.

[0006] Targeted recycling refers to a process of reusing a product after it has been scrapped, by rationally decomposing and recombining it to produce a similar product with the same or similar performance. Therefore, based on the principle of targeted recycling, providing a method for the resource utilization of refined phosphoric acid desulfurization residue is of great significance. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] This application provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. Compared with related technologies, the method provided by this application can prepare high-purity barium sulfate, ammonium sulfate and phosphoric acid, realize the recycling of materials, has a simple process, is easy to industrialize, and has high environmental benefits.

[0009] This application provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue, the method comprising the following steps:

[0010] The desulfurization residue and the leaching agent are first mixed to obtain a first suspension, wherein the leaching agent includes an organic solvent, and the organic solvent includes methyl isobutyl ketone and fatty alcohol;

[0011] The first suspension is filtered first to obtain the first filtrate;

[0012] The first filtrate is subjected to desulfurization treatment and second filtration in sequence to obtain the second filtrate;

[0013] The second filtrate was back-extracted to obtain phosphoric acid.

[0014] The method provided in this application uses refined phosphoric acid desulfurization residue as raw material, the main component of which is calcium sulfate, and also contains a small amount of barium sulfate, trace amounts of barium carbonate, calcium carbonate, and phosphates (such as calcium phosphate, barium phosphate, or magnesium iron aluminum phosphate). This application obtains high-purity and high-recovery phosphoric acid through operations such as leaching, first filtration, desulfurization treatment, second filtration, and back-extraction. This application uses methyl isobutyl ketone and fatty alcohol as leaching agents. Methyl isobutyl ketone is an organic solvent with a low boiling point (116℃) and low viscosity (0.5 mPa·s), which is easily evaporated and regenerated, and has good binding force to phosphoric acid. Fatty alcohol can form hydrogen bond structures with phosphoric acid, further enhancing the leaching ability of phosphoric acid. Simultaneously, fatty alcohol can act as an antifoaming agent, quickly eliminating bubbles generated during the leaching process and strengthening the mixing and washing effect, thereby greatly improving the leaching rate of phosphoric acid.

[0015] In one embodiment, the desulfurization slag is crushed before the first mixing.

[0016] In one embodiment, the average particle size of the crushed desulfurization slag is ≤0.1mm, for example, it can be 0.1mm, 0.09mm, 0.08mm or 0.07mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the volume ratio of methyl isobutyl ketone to fatty alcohol is (20-50):1, for example, it can be 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In one embodiment, the fatty alcohol includes any one or a combination of at least two of n-butanol, isobutanol, or isoamyl alcohol.

[0019] In one embodiment, the mass percentage of solids in the first suspension is 35-45%, for example, it can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] In one embodiment, pH adjustment is performed before the first filtration.

[0021] In one embodiment, the pH adjustment includes: mixing a first suspension and a pH adjuster and stirring.

[0022] In one embodiment, the pH adjuster comprises sulfuric acid.

[0023] In one embodiment, the mass percentage concentration of the sulfuric acid is ≥98%, for example, it can be 98.1%, 98.2%, 98.3%, 98.4% or 98.5%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In one embodiment, the stirring time during pH adjustment is 1-2 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In one embodiment, the endpoint of the pH adjustment is a pH value < 4, such as 3.9, 3.8, 3.7 or 3.6, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In one embodiment, the first filtrate is sequentially circulated, washed, and concentrated before the desulfurization treatment.

[0027] In one embodiment, the cyclic washing includes: returning the first filtrate to the first suspension, and then performing a first filtration until the first filtrate reaches the target specific gravity.

[0028] In one embodiment, the target specific gravity of the first filtrate after the cyclic washing is >0.85, for example, it can be 0.86, 0.87, 0.88, 0.89 or 0.9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In one embodiment, the mass percentage of phosphorus pentoxide in the first filtrate after the cyclic washing is 8-10%, for example, it can be 8%, 8.5%, 9%, 9.5% or 10%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] In one embodiment, the specific gravity of the concentrate obtained by concentration is 0.95-1, for example, it can be 0.95, 0.96, 0.97, 0.98, 0.98 or 1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] In one embodiment, the concentration of phosphorus pentoxide in the concentrate is 15-20% by mass, for example, it can be 15%, 16%, 17%, 18%, 19% or 20%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In one embodiment, the concentrated organic vapor is used to prepare an organic solvent, which is then reused in the first mixture.

[0033] In one embodiment, the desulfurizing agent used in the desulfurization treatment includes calcium carbonate and barium carbonate.

[0034] In one embodiment, the mass ratio of calcium carbonate to barium carbonate in the desulfurizing agent is (8-12):1, for example, it can be 8:1, 9:1, 10:1, 11:1 or 12:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] In one embodiment, the molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrate. 2- 110-150% of the molar amount, for example, 110%, 120%, 130%, 140% or 150%, but not limited to the listed values, and other unlisted values ​​within the range also apply.

[0036] In one embodiment, the desulfurization process includes adding a desulfurizing agent to the concentrate while stirring.

[0037] In this application, simultaneous stirring is preferred to increase the contact area between the desulfurizing agent and the concentrate, thereby preventing the desulfurizing agent from clumping.

[0038] In one embodiment, the time for adding the desulfurizing agent is 30-60 minutes, for example, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] In one embodiment, after adding the desulfurizing agent, stirring is continued for 20-40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] In one embodiment, the desulfurizing agent is added by first adding calcium carbonate and then adding barium carbonate.

[0041] In one embodiment, the back-extraction agent used in the back-extraction includes water.

[0042] In this application, the number of back-extraction stages is not specifically limited and can be selected as needed.

[0043] In one embodiment, the back-extraction temperature is 50-60°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In one embodiment, the ratio of the second filtrate to the stripping agent in the back-extraction is (3-6):1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1 or 6:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] In one embodiment, the organic phase obtained from the back-extraction is regenerated to obtain an organic solvent, which is then reused in the first mixture.

[0046] In this application, the regenerator used for regeneration is not particularly limited and can be any regenerator commonly used in the art, such as sodium hydroxide or sodium carbonate solution.

[0047] In one embodiment, the first filter also produces a first filter residue.

[0048] In one embodiment, the first filter residue and ammonium sulfate solution are mixed a second time to obtain a second suspension.

[0049] In one embodiment, excess ammonia and excess carbon dioxide are sequentially introduced into the second suspension, followed by a third filtration to obtain barium sulfate and a third filtrate.

[0050] In one embodiment, the third filtrate is heated and then filtered a fourth time to obtain a calcium carbonate and ammonium sulfate solution.

[0051] In this application, the first filter residue contains calcium sulfate and barium sulfate. Excess ammonia is used to make the second suspension alkaline. Carbon dioxide is used to first convert calcium sulfate into calcium carbonate, and then further convert calcium bicarbonate into calcium carbonate. After that, barium sulfate and a third filtrate containing calcium bicarbonate are obtained through a third filtration. The third filtrate is heated to decompose and obtain carbon dioxide and calcium carbonate. After a fourth filtration, calcium carbonate and ammonium sulfate solution are obtained.

[0052] In one embodiment, the first filter residue is dried before the second mixing.

[0053] In one embodiment, the drying temperature is 80-100°C, for example, it can be 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In one embodiment, the drying time is 30-60 minutes, for example, it can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] In one embodiment, the organic vapor obtained from the drying process is used to prepare an organic solvent, which is then reused in the first mixture.

[0056] In one embodiment, water is also added to the second mixture.

[0057] In one embodiment, the volume ratio of ammonium sulfate solution to water in the second mixture is (4-6):1, for example, it can be 4:1, 4.2:1, 4.5:1, 4.8:1, 5:1, 5.2:1, 5.5:1, 5.8:1 or 6:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In one embodiment, the mass percentage concentration of the ammonium sulfate solution used in the second mixture is 38-40%, for example, it can be 38%, 38.2%, 38.5%, 38.8%, 39%, 39.2%, 39.5%, 39.8% or 40%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0059] In one embodiment, the temperature of the second mixture is 50-60°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] In one embodiment, the mass percentage of solids in the second suspension is 30-40%, for example, it can be 30%, 32%, 34%, 36%, 38% or 40%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In one embodiment, the pH value of the second suspension after the excess ammonia gas is introduced is ≥12, for example, it can be 12, 12.5 or 13, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] In one embodiment, the excess carbon dioxide is introduced for 1-2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In one embodiment, the heating temperature is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 78°C, 79°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In one embodiment, the carbon dioxide generated by heating is reused in the second suspension.

[0065] In one embodiment, the calcium carbonate is reused to prepare desulfurization slag.

[0066] In this application, the calcium carbonate can be returned to the desulfurization section for desulfurization to obtain desulfurization slag.

[0067] In one embodiment, the ammonium sulfate solution obtained from the fourth filtration is sequentially evaporated and concentrated, cooled and crystallized, and then filtered a fifth time to obtain ammonium sulfate crystals and ammonium sulfate mother liquor.

[0068] In one embodiment, the evaporation and concentration temperature is 105-107°C, for example, it can be 105°C, 105.5°C, 106°C, 106.5°C or 107°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In one embodiment, the cooling rate for the cooling crystallization is 3-4°C / min, for example, it can be 3°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min or 4°C / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In one embodiment, the ammonia gas obtained from the evaporation and concentration is reused in the second suspension.

[0071] In one embodiment, the ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare an ammonium sulfate solution, which is then reused in the second mixture.

[0072] As a preferred technical solution of this application, the method includes the following steps:

[0073] After crushing the desulfurization slag to an average particle size ≤0.1mm, the desulfurization slag and leaching agent are mixed for the first time to obtain a first suspension. The leaching agent is prepared by mixing methyl isobutyl ketone and fatty alcohol in a volume ratio of (20-50):1. The mass percentage of solids in the first suspension is 35-45%. The first suspension is mixed with sulfuric acid with a mass percentage concentration ≥98% and stirred for 1-2 hours to adjust the pH value to <4. Then, the first filtration is performed to obtain a first filtrate and a first filter residue.

[0074] The first filtrate is circulated and washed, the circulated washing comprising: returning the first filtrate to the first suspension, and then performing a first filtration until the specific gravity of the first filtrate is >0.85, and the mass percentage of phosphorus pentoxide in the first filtrate after the circulated washing is 8-10%; then, the first filtrate after the circulated washing is concentrated to obtain a concentrated solution, the specific gravity of the concentrated solution is 0.95-1, and the mass percentage of phosphorus pentoxide in the concentrated solution is 15-20%, the organic vapor obtained from the concentration is used to prepare an organic solvent, and then reused in the first mixture; a desulfurizing agent is added to the concentrated solution, the time for adding the desulfurizing agent is 30-60 min, and then stirring is continued for 20-40 min for desulfurization treatment, the desulfurizing agent is calcium carbonate and barium carbonate with a mass ratio of (8-12):1, and the molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrated solution. 2- The molar amount is 110-150%, and then a second filtration is performed to obtain a second filtrate; the second filtrate is back-extracted with water at a temperature of 50-60°C, and the ratio of the second filtrate to water in the back-extraction is (3-6):1, to obtain phosphoric acid; the organic phase obtained by back-extraction is regenerated to obtain an organic solvent, which is then reused in the first mixture;

[0075] The first filter residue is dried at 80-100℃ for 30-60 minutes. The organic vapor obtained from the drying is used to prepare an organic solvent and then recycled in the first mixture. Then, the first filter residue, ammonium sulfate solution, and water are mixed again at 50-60℃ to obtain a second suspension. The solid content in the second suspension is 30-40% by mass, and the volume ratio of ammonium sulfate solution to water in the second mixture is (4-6):1. The mass concentration of the ammonium sulfate solution is 38-40%. Afterward, excess ammonia is introduced into the second suspension until the pH value is ≥12, followed by the introduction of excess carbon dioxide for 1-2 hours, and then a third mixture is prepared. The mixture is filtered to obtain barium sulfate and a third filtrate. The third filtrate is heated at 70-80°C, and the carbon dioxide generated is recycled into the second suspension. Then, a fourth filtration is performed to obtain calcium carbonate and ammonium sulfate solution. The calcium carbonate is recycled to prepare desulfurization slag. The ammonium sulfate solution obtained from the fourth filtration is evaporated and concentrated at 105-107°C, then cooled and crystallized at a cooling rate of 3-4°C / min. A fifth filtration is performed to obtain ammonium sulfate crystals and ammonium sulfate mother liquor. The ammonia gas obtained from the evaporation and concentration is recycled into the second suspension. The ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare ammonium sulfate solution and recycled into the second mixture.

[0076] Compared with related technologies, the embodiments of this application have the following beneficial effects:

[0077] (1) The method provided in this application uses refined phosphoric acid desulfurization residue as raw material. Except for a small amount of reagents such as sulfuric acid that need to be added, the organic solvents, carbon dioxide, calcium carbonate, ammonia and ammonium sulfate in the reaction process can be recycled in the reaction process. No waste is generated, which has high environmental benefits.

[0078] (2) The method provided in this application uses a combination of methyl isobutyl ketone and fatty alcohol as an extractant, which can improve the binding force of phosphoric acid and at the same time increase the mixing effect by defoaming, thereby improving the recovery rate and purity of phosphoric acid.

[0079] (3) The method provided in this application embodiment can realize the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue, and obtain phosphoric acid with high recovery rate as well as high-purity barium sulfate, ammonium sulfate and phosphoric acid, which can be used to produce downstream products with higher added value and have broad market prospects.

[0080] (4) The method provided in this application has simple raw material pretreatment, low cost, mild reaction conditions, simple and easy production process, low energy consumption, no environmental pollutants, and is easy to industrialize.

[0081] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0082] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0083] Figure 1 This is a flowchart of the method described in Embodiment 1 of this application. Detailed Implementation

[0084] Example 1

[0085] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The desulfurization residue used in this embodiment comprises, by mass percentage: 95% calcium sulfate, 4.5% barium sulfate, 0.2% calcium carbonate, 0.25% phosphate, and 0.05% barium carbonate. Figure 1 As shown, the method includes the following steps:

[0086] After the desulfurization slag is crushed to an average particle size of 0.1 mm, the desulfurization slag and the leaching agent are mixed for the first time to obtain a first suspension. The leaching agent is prepared by mixing methyl isobutyl ketone and n-butanol at a volume ratio of 20:1. The mass percentage of solids in the first suspension is 35%. The first suspension is mixed with sulfuric acid with a mass percentage concentration of 98.5% and stirred for 1.5 h to adjust the pH value to 3.8. Then, the first filtration is performed to obtain a first filtrate and a first filter residue.

[0087] The first filtrate is circulated and washed, the circulated washing comprising: returning the first filtrate to the first suspension, and then performing a first filtration until the specific gravity of the first filtrate is 0.85, and the mass percentage of phosphorus pentoxide in the first filtrate after the circulated washing is 8%; then, the first filtrate after the circulated washing is concentrated to obtain a concentrated solution, the specific gravity of the concentrated solution is 0.95, and the mass percentage of phosphorus pentoxide in the concentrated solution is 15%, the organic vapor obtained from the concentration is used to prepare an organic solvent, and then recycled back to the first mixture; a desulfurizing agent is added to the concentrated solution, the addition time of the desulfurizing agent is 30 min, and then stirring is continued for 30 min for desulfurization treatment, the desulfurizing agent is calcium carbonate and barium carbonate in a mass ratio of 8:1, and the molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrated solution. 2- The molar amount is 110%, and then a second filtration is performed to obtain a second filtrate; the second filtrate is back-extracted with water at a temperature of 50°C, and the ratio of the second filtrate to water in the back-extraction is 3:1 to obtain phosphoric acid. The organic phase obtained from the back-extraction is regenerated with 5% sodium hydroxide to obtain an organic solvent, which is then reused in the first mixture.

[0088] The first filter residue was dried at 90°C for 50 minutes. The organic vapor obtained from the drying was used to prepare an organic solvent and then recycled back into the first mixture. Next, the first filter residue, ammonium sulfate solution, and water were mixed again at 50°C to obtain a second suspension. The second suspension contained 30% solids by mass, and the volume ratio of ammonium sulfate solution to water in the second mixture was 4:1. The mass concentration of the ammonium sulfate solution was 38%. Then, excess ammonia was introduced into the second suspension until the pH reached 12, followed by the introduction of excess carbon dioxide for 1 hour. Finally, a third filtration was performed to obtain sulfur... Barium sulfate and a third filtrate; the third filtrate is heated at 70°C, and the carbon dioxide generated by heating is recycled into the second suspension, followed by a fourth filtration to obtain calcium carbonate and ammonium sulfate solution; the calcium carbonate is recycled to prepare desulfurization slag; the ammonium sulfate solution obtained from the fourth filtration is evaporated and concentrated at 105°C, then cooled and crystallized at a cooling rate of 3°C / min, followed by a fifth filtration to obtain ammonium sulfate crystals and ammonium sulfate mother liquor, the ammonia gas obtained from the evaporation and concentration is recycled into the second suspension, and the ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare ammonium sulfate solution and recycled into the second mixture.

[0089] Example 2

[0090] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The desulfurization residue used in this embodiment is the same as that in Embodiment 1. The method includes the following steps:

[0091] After the desulfurization slag is crushed to an average particle size of 0.08 mm, the desulfurization slag and leaching agent are mixed for the first time to obtain a first suspension. The leaching agent is prepared by mixing methyl isobutyl ketone and isobutanol at a volume ratio of 35:1. The mass percentage of solids in the first suspension is 40%. The first suspension is mixed with sulfuric acid with a mass percentage concentration of 98.5% and stirred for 1 hour to adjust the pH value to 3.9. Then, the first filtration is performed to obtain a first filtrate and a first filter residue.

[0092] The first filtrate is circulated and washed, the circulated washing comprising: returning the first filtrate to the first suspension, and then performing a first filtration until the specific gravity of the first filtrate is 0.87, and the mass percentage of phosphorus pentoxide in the first filtrate after the circulated washing is 9%; then, the first filtrate after the circulated washing is concentrated to obtain a concentrated solution, the specific gravity of the concentrated solution is 0.97, and the mass percentage of phosphorus pentoxide in the concentrated solution is 17%, the organic vapor obtained from the concentration is used to prepare an organic solvent, and then recycled back to the first mixture; a desulfurizing agent is added to the concentrated solution, the addition time of the desulfurizing agent is 45 min, and then stirring is continued for 20 min for desulfurization treatment, the desulfurizing agent is calcium carbonate and barium carbonate with a mass ratio of 10:1, and the molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrated solution. 2- The molar amount is 130%, and then a second filtration is performed to obtain a second filtrate; the second filtrate is back-extracted with water at a temperature of 55°C, and the ratio of the second filtrate to water in the back-extraction is 4:1 to obtain phosphoric acid. The organic phase obtained from the back-extraction is regenerated with a 15% sodium carbonate solution to obtain an organic solvent, which is then reused in the first mixture.

[0093] The first filter residue was dried at 80°C for 60 minutes. The organic vapor obtained from the drying was used to prepare an organic solvent and then recycled back into the first mixture. Then, the first filter residue, ammonium sulfate solution, and water were mixed again at 55°C to obtain a second suspension. The second suspension had a solid content of 35% by mass, and the volume ratio of ammonium sulfate solution to water in the second mixture was 5:1. The mass percentage concentration of the ammonium sulfate solution was 39%. Afterward, excess ammonia was introduced into the second suspension until the pH value reached 12.2, followed by the introduction of excess carbon dioxide for 1.5 hours. A third filtration was then performed to obtain… Barium sulfate and a third filtrate; the third filtrate is heated at 75°C, and the carbon dioxide generated is recycled into the second suspension, followed by a fourth filtration to obtain a calcium carbonate and ammonium sulfate solution; the calcium carbonate is recycled to prepare desulfurization slag; the ammonium sulfate solution obtained from the fourth filtration is evaporated and concentrated at 106°C, then cooled and crystallized at a cooling rate of 3.5°C / min, followed by a fifth filtration to obtain ammonium sulfate crystals and ammonium sulfate mother liquor; the ammonia gas obtained from the evaporation and concentration is recycled into the second suspension, and the ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare an ammonium sulfate solution and recycled into the second mixture.

[0094] Example 3

[0095] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The desulfurization residue used in this embodiment is the same as that in Embodiment 1. The method includes the following steps:

[0096] After the desulfurization slag is crushed to an average particle size of 0.07 mm, the desulfurization slag and leaching agent are mixed for the first time to obtain a first suspension. The leaching agent is prepared by mixing methyl isobutyl ketone and ethanol at a volume ratio of 50:1. The mass percentage of solids in the first suspension is 45%. The first suspension is mixed with sulfuric acid with a mass percentage concentration of 98.5% and stirred for 2 hours to adjust the pH value to 3.7. Then, the first filtration is performed to obtain a first filtrate and a first filter residue.

[0097] The first filtrate is circulated and washed, the circulated washing comprising: returning the first filtrate to the first suspension, and then performing a first filtration until the specific gravity of the first filtrate is 0.9, and the mass percentage of phosphorus pentoxide in the first filtrate after the circulated washing is 10%; then, the first filtrate after the circulated washing is concentrated to obtain a concentrated solution, the specific gravity of the concentrated solution is 1.0, and the mass percentage of phosphorus pentoxide in the concentrated solution is 20%, the organic vapor obtained from the concentration is used to prepare an organic solvent, and then reused in the first mixture; a desulfurizing agent is added to the concentrated solution, the addition time of the desulfurizing agent is 60 min, and then stirring is continued for 40 min for desulfurization treatment, the desulfurizing agent is calcium carbonate and barium carbonate with a mass ratio of 12:1, and the molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrated solution. 2- The molar amount is 150%, and then a second filtration is performed to obtain a second filtrate; the second filtrate is back-extracted with water at a temperature of 60°C, and the ratio of the second filtrate to water in the back-extraction is 6:1 to obtain phosphoric acid. The organic phase obtained from the back-extraction is regenerated with a 15% sodium carbonate solution to obtain an organic solvent, which is then reused in the first mixture.

[0098] The first filter residue was dried at 100°C for 30 minutes. The organic vapor obtained from the drying was used to prepare an organic solvent and then recycled back into the first mixture. Then, the first filter residue, ammonium sulfate solution, and water were mixed again at 60°C to obtain a second suspension. The second suspension had a solid content of 40% by mass, and the volume ratio of ammonium sulfate solution to water in the second mixture was 6:1, with the ammonium sulfate solution having a mass concentration of 40%. Afterward, excess ammonia was introduced into the second suspension until the pH value reached 12.3, followed by the introduction of excess carbon dioxide for 2 hours. A third filtration was then performed to obtain… Barium sulfate and a third filtrate; the third filtrate is heated at 80°C, and the carbon dioxide generated is recycled into the second suspension, followed by a fourth filtration to obtain a calcium carbonate and ammonium sulfate solution; the calcium carbonate is recycled to prepare desulfurization slag; the ammonium sulfate solution obtained from the fourth filtration is evaporated and concentrated at 107°C, then cooled and crystallized at a cooling rate of 4°C / min, followed by a fifth filtration to obtain ammonium sulfate crystals and ammonium sulfate mother liquor; the ammonia gas obtained from the evaporation and concentration is recycled into the second suspension, and the ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare an ammonium sulfate solution and recycled into the second mixture.

[0099] Example 4

[0100] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The only difference from Example 1 is that the volume ratio of methyl isobutyl ketone and n-butanol is 10:1.

[0101] Example 5

[0102] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The only difference from Example 1 is that the volume ratio of methyl isobutyl ketone and n-butanol is 60:1.

[0103] Example 6

[0104] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The only difference from Embodiment 1 is that the mass ratio of calcium carbonate to barium carbonate is 5:1.

[0105] Example 7

[0106] This embodiment provides a method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue. The only difference between this embodiment and Example 1 is that the mass ratio of calcium carbonate to barium carbonate is 15:1.

[0107] Comparative Example 1

[0108] This comparative example provides a method for the resource utilization of refined phosphoric acid desulfurization residue. The only difference between this method and Example 1 is that the leaching agent is replaced with an equal volume of water.

[0109] Comparative Example 2

[0110] This comparative example provides a method for the resource utilization of refined phosphoric acid desulfurization residue. The only difference from Example 1 is that methyl isobutyl ketone is replaced with an equal volume of n-butanol.

[0111] Comparative Example 3

[0112] This comparative example provides a method for the resource utilization of refined phosphoric acid desulfurization residue. The only difference from Example 1 is that n-butanol is replaced with an equal volume of methyl isobutyl ketone.

[0113] The recovery rates of phosphoric acid in Examples 1-7 and Comparative Examples 1-3 were determined using the method specified in JC / T 2073-2011, and the results are shown in Table 1.

[0114] The impurity content of phosphoric acid in Examples 1-7 and Comparative Examples 1-3 was determined using the method specified in HG / T 4069-2008, as shown in Table 1.

[0115] The purity of phosphoric acid, barium sulfate, and ammonium sulfate in Examples 1-7 and Comparative Examples 1-3 was determined by HG / T 4069-2008, GB / T2899-2008, and GB / T29206-2012, respectively. The results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] The following points can be observed from the data in Table 1:

[0120] (1) As can be seen from the data in Examples 1-7, the method provided in this application can achieve a phosphoric acid recovery rate of over 98.30%, an impurity content of phosphoric acid of less than 0.0009 wt%, a barium sulfate purity of over 99.08 wt%, and an ammonium sulfate purity of over 99.32 wt%. Under preferred conditions, the phosphoric acid recovery rate can reach over 95.32%, the impurity content of phosphoric acid of less than 0.0008 wt%, the barium sulfate purity of over 99.32 wt%, and the ammonium sulfate purity of over 99.68 wt%.

[0121] (2) A comprehensive comparison of the data from Examples 1 and 4-5 shows that the volume ratio of methyl isobutyl ketone to n-butanol in Example 1 is 20:1, which is significantly higher than the 10:1 and 60:1 ratios in Examples 4-5, respectively. Therefore, it can be seen that controlling the volume ratio of methyl isobutyl ketone to n-butanol in this application can further improve the recovery rate of phosphoric acid.

[0122] (3) A comprehensive comparison of the data from Examples 1 and 6-7 shows that the mass ratio of calcium carbonate to barium carbonate in Example 1 is 8:1, which is significantly higher than the 5:1 and 15:1 ratios in Examples 6-7. Therefore, it is evident that controlling the mass ratio of calcium carbonate to barium carbonate in this application can further improve the purity of barium sulfate and ammonium sulfate.

[0123] (4) A comprehensive comparison of the data from Example 1 and Comparative Examples 1-3 shows that, in Example 1, methyl isobutyl ketone and n-butanol were used as leaching agents. Compared with Comparative Examples 1-3, which used only water, n-butanol and methyl isobutyl ketone as leaching agents respectively, the recovery rate of phosphoric acid in Example 1 was significantly higher than that in Comparative Examples 1-3, and the impurity content in Example 1 was significantly lower than that in Comparative Example 1. Therefore, it can be seen that the leaching agent of methyl isobutyl ketone and n-butanol used in this application can further improve the recovery rate of phosphoric acid and reduce the impurity content.

[0124] In summary, the method provided in this application can prepare high-purity barium sulfate, ammonium sulfate, and phosphoric acid, enabling the recycling of materials. The process is simple, easy to industrialize, and has high economic and environmental benefits.

Claims

1. A method for the targeted recycling and resource utilization of refined phosphoric acid desulfurization residue, comprising the following steps: The desulfurization residue and the leaching agent are first mixed to obtain a first suspension, wherein the leaching agent includes an organic solvent, and the organic solvent includes methyl isobutyl ketone and fatty alcohol; The first suspension is filtered first to obtain the first filtrate; The first filtrate is subjected to desulfurization treatment and second filtration in sequence to obtain the second filtrate; The second filtrate was back-extracted to obtain phosphoric acid; The first filtration also yields a first filter residue; The first filter residue and ammonium sulfate solution are mixed a second time to obtain a second suspension; Excess ammonia and excess carbon dioxide are sequentially introduced into the second suspension, followed by a third filtration to obtain barium sulfate and a third filtrate. The third filtrate is then heated and filtered a fourth time to obtain a calcium carbonate and ammonium sulfate solution.

2. The method according to claim 1, wherein, The desulfurization slag is crushed before the first mixing.

3. The method according to claim 2, wherein, The average particle size of the desulfurization residue after crushing is ≤0.1mm.

4. The method according to claim 1, wherein, The volume ratio of methyl isobutyl ketone to fatty alcohol is (20-50):

1.

5. The method according to claim 1, wherein, The fatty alcohols include any one or a combination of at least two of n-butanol, isobutanol, or isoamyl alcohol.

6. The method according to claim 1, wherein, The mass percentage of solids in the first suspension is 35-45%.

7. The method according to claim 1, wherein, pH adjustment is performed before the first filtration.

8. The method according to claim 7, wherein, The pH adjustment includes: mixing the first suspension and the pH adjuster and stirring.

9. The method according to claim 8, wherein, The pH adjuster includes sulfuric acid.

10. The method according to claim 9, wherein, The sulfuric acid has a mass percentage concentration of ≥98%.

11. The method according to claim 8, wherein, The stirring time for pH adjustment is 1-2 hours.

12. The method according to claim 7, wherein, The endpoint of the pH adjustment is a pH value < 4.

13. The method according to claim 1, wherein, Before the desulfurization treatment, the first filtrate is sequentially circulated, washed, and concentrated.

14. The method according to claim 13, wherein, The cyclic washing includes: returning the first filtrate to the first suspension, and then performing a first filtration until the first filtrate reaches the target specific gravity.

15. The method according to claim 14, wherein, The target specific gravity of the first filtrate after the cyclic washing is >0.

85.

16. The method according to claim 13, wherein, The mass percentage of phosphorus pentoxide in the first filtrate after the cyclic washing is 8-10%.

17. The method according to claim 13, wherein, The specific gravity of the concentrated solution obtained by the concentration is 0.95-1.

18. The method according to claim 17, wherein, The concentrate contains 15-20% phosphorus pentoxide by mass.

19. The method according to claim 13, wherein, The concentrated organic vapor is used to prepare an organic solvent, which is then reused in the first mixture.

20. The method of claim 17, wherein, The desulfurizing agents used in the desulfurization process include calcium carbonate and barium carbonate.

21. The method according to claim 20, wherein, The mass ratio of calcium carbonate to barium carbonate in the desulfurizing agent is (8-12):

1.

22. The method according to claim 20, wherein, The molar amount of the desulfurizing agent is equal to the amount of SO4 in the concentrate. 2- 110-150% of the molar weight.

23. The method according to claim 17, wherein, The desulfurization process includes adding a desulfurizing agent to the concentrate while stirring.

24. The method according to claim 23, wherein, The desulfurizing agent is added at a time of 30-60 minutes.

25. The method according to claim 23, wherein, After adding the desulfurizing agent, continue stirring for 20-40 minutes.

26. The method according to claim 23, wherein, The desulfurizing agent is added by first adding calcium carbonate and then adding barium carbonate.

27. The method according to claim 1, wherein, The stripping agent used in the stripping process includes water.

28. The method according to claim 1, wherein, The back-extraction temperature is 50-60℃.

29. The method according to claim 1, wherein, The ratio of the second filtrate to the stripping agent in the back-extraction process is (3-6):

1.

30. The method according to claim 1, wherein, The organic phase obtained from the back-extraction is regenerated to obtain an organic solvent, which is then reused in the first mixture.

31. The method according to claim 1, wherein, The first filter residue is dried before the second mixing.

32. The method according to claim 31, wherein, The drying temperature is 80-100℃.

33. The method according to claim 31, wherein, The drying time is 30-60 minutes.

34. The method according to claim 31, wherein, The organic vapor obtained from the drying process is used to prepare an organic solvent, which is then reused in the first mixture.

35. The method according to claim 1, wherein, Water is also added to the second mixture.

36. The method according to claim 35, wherein, The volume ratio of ammonium sulfate solution to water in the second mixture is (4-6):

1.

37. The method according to claim 1, wherein, The mass percentage concentration of the ammonium sulfate solution used in the second mixture is 38-40%.

38. The method according to claim 1, wherein, The temperature of the second mixture is 50-60℃.

39. The method according to claim 1, wherein, The mass percentage of solids in the second suspension is 30-40%.

40. The method according to claim 1, wherein, The pH value of the second suspension after the excess ammonia gas is introduced is ≥12.

41. The method according to claim 1, wherein, The excess carbon dioxide is introduced over a period of 1-2 hours.

42. The method according to claim 1, wherein, The heating temperature is 70-80℃.

43. The method according to claim 1, wherein, The carbon dioxide generated by heating is reused in the second suspension.

44. The method according to claim 1, wherein, The ammonium sulfate solution obtained from the fourth filtration is subjected to evaporation and concentration, cooling and crystallization, and a fifth filtration to obtain ammonium sulfate crystals and ammonium sulfate mother liquor.

45. The method according to claim 44, wherein, The evaporation and concentration temperature is 105-107℃.

46. ​​The method of claim 44, wherein, The cooling rate for the cooling crystallization is 3-4℃ / min.

47. The method of claim 44, wherein, The ammonia gas obtained from evaporation and concentration is reused in the second suspension.

48. The method according to claim 44, wherein, The ammonium sulfate mother liquor obtained from the fifth filtration is used to prepare an ammonium sulfate solution, which is then reused in the second mixture.

Images